In the past, owing to higher densities using shorter wavelengths of semiconductor lasers and higher numerical apertures (NA) of objective lenses, greater capacities from CD to DVD and then to Blu-ray Disc (Trademark) have been accomplished. In recent years, however, the trend is toward creating multiple layers rather than higher densities to achieve greater capacities. BDXL (Trademark) has been standardized. That is, BD discs having multiple layers have been created. A BD disc having 33 GB per layer and achieving 100 GB with three layers is available. Furthermore, a BD disc having 32 GB per layer and achieving 128 GB with four layers is available. Because broadcast media have evolved and there are increasing amounts of moving picture contents, amounts of data handled by individuals and enterprises have continued to increase. It can be expected that there will be a demand for storage media having greater capacities in the future. One method available for achieving greater capacities consists of making laser light enter from both surfaces of an optical disc and forming recording layers on both front and rear surfaces of the disc. In optical discs, fingerprints and dust on the recording surfaces may affect the quality of signal when recording or playback is made. In some cases, cartridges are used to prevent adhesion of fingerprints and dust on the recording surfaces.
As set forth in Patent literature 1, a region known as a burst cutting area (hereinafter referred to as the BCA) is formed on the inner side of an optical disc such as CD, DVD, or Blu-ray Disc (Trademark). Optical disc drives, players, and recorders are required to provide reading compatibility with various discs. It has become increasingly difficult to discriminate discs. One means to discriminate discs is to contain information intrinsic to each disc within the BCA of the disc. The BCA is not essential to the existing DVD disc using a laser of a wavelength of 650 nm. However, in the Blu-ray Disc (Trademark) using a laser of a wavelength of 405 nm, information about individual identification codes and disc copy protection is included and so the BCA has become more important and is an essential item of the disc. On the other hand, Patent reference 2 discloses that the lead-in area on the inner side of a recordable Blu-ray Disc (Trademark), i.e., BD-RE, is partitioned into a first guard area (Guard 1), a PIC (Permanent Information & Control data) area, a second guard area (Guard 2), information 2 area (Info 2), an OPC (Optimum Power Control) area, and other areas. Furthermore, it is set forth that the PIC area is used as a region previously recorded with data.